Burners of the type hereinafter referred to are normally utilized in a gasifier unit wherein a synthetic gas is manufactured by partial oxidation of a fossil fuel at a relatively high pressure. The gasifier operating pressure of between about 350 psi and 1200 psi is normally maintained, at a temperature between 1700.degree. F. and 3100.degree. F. Thus, the burner which is positioned within the gasifier combustion chamber is subjected to harsh operating conditions.
Operationally, one embodiment of such a gasification system comprises a gasifier having a combustion chamber into which a coal or coke fuel mixture or slurry is injected. The injection member comprises a burner which receives and mixes flows of particulated fuel, and an oxidizing gas. The mixture is then forcibly injected into the combustion chamber to overcome the high pressure generated in the latter.
Unless the burner, which partially intrudes into the gasifier combustion chamber, is provided with adequate cooling, it will soon become damaged or even inoperative.
It is customary therefore to provide gasifier burners with a cooling system that protects the burner external exposed surfaces. A cooling system found to suit this purpose would comprise a series of coils which encircle and contact the lower or discharge portion of the burner. A coolant, preferably water, is circulated through this coil system at a sufficient pressure and rate to maintain the burner tip at a reasonable operating temperature.
When adequate cooling is achieved, the burner's function will not be adversely affected, nor will it suffer thermal damage.
The cooling coils are usually formed of steel, and are close fitting about the burner's outer surface. These cooling coils, are communicated with a pressurized source of the coolant. Thus, water flow through the cooling system can be regulated to maintain a desired burner tip temperature.
Since the cooling coils are of necessity positioned within the gasifier combustion chamber, any damage to the coils in the form of a pin hole, crack, or break, will discharge water into the gasifier combustion chamber.
In such an instance, unless the gasifier operation is immediately discontinued, a probability exists that the burner and even the gasifier could be damaged to the point where either will become unusable.
Usual damage to the cooling system could consist of a minor crack within the cooling coils or around the burner surface exposed to the hot combustion gases. It can, however, consist of a major break or rupture in either the coils or the burner. In one instance, the coolant water will be discharged into the gasifier at a relatively minor rate with minimal effect. The break will thus not be readily detected. Where a major break occurs however, a large amount of water will be discharged into the gasifier.
It is desirable in any instance, that the temperature and flow of water through the cooling system be constantly monitored. This function is necessary if one is to promptly detect any form of break or water leakage.
If compensating steps are taken promptly, after a break does occur, the gasifier operation can be controllably discontinued and the burner protected from severe damage. However, under certain circumstances interruption of minor coolant flow might not be detected. The burner operation will therefore continue, and the gasifier will operate until the coolant leak has become so severe as to result in excessive damage.
In the presently disclosed arrangement, a unique burner cooling system is provided which operates in two phases or modes. In the first phase, a high pressure flow of water is circulated through a cooling element to the burner tip. Concurrently, conditions of the coolant flow are monitored by a continuous sensing of the pressure differential which occurs between the coolant stream, and a standard pressure point exterior to the gasifier.
When it becomes apparent through monitoring of the system that a break has occurred in the cooling element, the second phase or mode of the system is selectively actuated. The latter functions to inject a second source of high pressure coolant water into the cooling system. This step will preclude the possible back flow of high pressure gas from the gasifier combustion chamber, through cooling system piping.
It is therefore an object of the invention to provide a burner cooling system which embodies a relatively fail safe operation.
A further object of the invention is to provide a burner cooling system in a high pressure gasifier unit which will be automatically actuated to adjust cooling water flow to avoid damage to the burner when the coolant system has become flawed through leakage.
A still further object of the invention is to provide a cooling system for a burner operating in a high pressure atmosphere, such system including a first phase that normally functions at a sufficiently high pressure and flow rate to cool the burner, and a second or emergency phase which is automatically actuated to supplement the first phase flow of cooling liquid whereby to avoid leakage of gas from the gasifier into the atmosphere.